Rockwell Automation 1775-KA PLC-3 Communication Adapter Module User Manual - Manual (Page 22)

Installation
Chapter 2
2Ć10
Interfacing a PLC–3 controller as a slave station on a multipoint
modem link (Figure 2.7)
Figure 2.7
Linking a PLC-3 to a Multi-drop Modem Link
Modem
1775-KA Module
10008–I
PLC-3 Controller
Multidrop Modem
Computer
Master Station
Multidrop Modem Link
Slave Stations
The first four applications above use the module’s RS–232–C port in the
unpolled mode, while the last application uses the polled mode. You can
select the mode of operation and other characteristics of the RS–232–C
port through the LIST function.